fix: preprompt would show after loading session (#8744)

Signed-off-by: Matt Toohey <contact@matttoohey.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/goose2/src/shared/api/acp.ts

@@ -73,12 +73,15 @@ export async function acpSendMessage(
     throw new Error("Session not prepared. Call acpPrepareSession first.");
   }
 
-  const hasSystem = systemPrompt && systemPrompt.trim().length > 0;
-  const effectivePrompt = hasSystem
-    ? `<persona-instructions>\n${systemPrompt}\n</persona-instructions>\n\n<user-message>\n${prompt}\n</user-message>`
-    : prompt;
-
-  const content: ContentBlock[] = [{ type: "text", text: effectivePrompt }];
+  const content: ContentBlock[] = [];
+  if (systemPrompt?.trim()) {
+    content.push({
+      type: "text",
+      text: systemPrompt,
+      annotations: { audience: ["assistant"] },
+    });
+  }
+  content.push({ type: "text", text: prompt });
   if (images) {
     for (const [data, mimeType] of images) {
       content.push({ type: "image", data, mimeType } as ContentBlock);

ui/goose2/src/shared/api/acpNotificationHandler.ts

@@ -10,6 +10,7 @@ import {
   findLatestUnpairedToolRequest,
 } from "@/features/chat/hooks/replayBuffer";
 import type {
+  TextContent,
   ToolRequestContent,
   ToolResponseContent,
 } from "@/shared/types/messages";
@@ -196,32 +197,32 @@ function handleReplay(sessionId: string, update: SessionUpdate): void {
     }
 
     case "user_message_chunk": {
+      if (update.content.type !== "text" || !("text" in update.content)) break;
       const messageId = update.messageId ?? crypto.randomUUID();
       const buffer = ensureReplayBuffer(sessionId);
       const existing = getBufferedMessage(sessionId, messageId);
+      // biome-ignore lint/suspicious/noExplicitAny: wire format has annotations but SDK types don't
+      const rawAnn = (update.content as any).annotations;
+      const ann: TextContent["annotations"] | undefined =
+        typeof rawAnn === "object" && rawAnn !== null ? rawAnn : undefined;
+      // Drop assistant-only blocks so they never enter chat state.
       if (
-        !existing &&
-        update.content.type === "text" &&
-        "text" in update.content
-      ) {
+        ann?.audience &&
+        ann.audience.length > 0 &&
+        !ann.audience.includes("user")
+      )
+        break;
+      const textBlock = makeTextBlock(update.content.text, ann);
+      if (!existing) {
         buffer.push({
           id: messageId,
           role: "user",
           created: Date.now(),
-          content: [{ type: "text", text: update.content.text }],
+          content: [textBlock],
           metadata: { userVisible: true, agentVisible: true },
         });
-      } else if (
-        existing &&
-        update.content.type === "text" &&
-        "text" in update.content
-      ) {
-        const last = existing.content[existing.content.length - 1];
-        if (last?.type === "text") {
-          (last as { type: "text"; text: string }).text += update.content.text;
-        } else {
-          existing.content.push({ type: "text", text: update.content.text });
-        }
+      } else {
+        existing.content.push(textBlock);
       }
       break;
     }
@@ -486,6 +487,13 @@ function findStreamingMessageId(sessionId: string): string | null {
     .streamingMessageId;
 }
 
+function makeTextBlock(
+  text: string,
+  ann?: TextContent["annotations"],
+): TextContent {
+  return { type: "text", text, ...(ann ? { annotations: ann } : {}) };
+}
+
 function findMessageInBuffer(
   sessionId: string,
   _toolCallId: string,

ui/goose2/src/shared/types/messages.ts

@@ -33,10 +33,19 @@ export type ChatAttachmentDraft =
 // Message roles
 export type MessageRole = "user" | "assistant" | "system";
 
+/** ACP audience restriction — which roles may see a content block. */
+export type Audience = ("user" | "assistant")[];
+
+/** ACP content-block annotations (mirrors the SDK's Annotations shape). */
+export interface ContentAnnotations {
+  audience?: Audience;
+}
+
 // Content block types
 export interface TextContent {
   type: "text";
   text: string;
+  annotations?: ContentAnnotations;
 }
 
 export interface ImageContent {
@@ -44,6 +53,7 @@ export interface ImageContent {
   source:
     | { type: "base64"; mediaType: string; data: string }
     | { type: "url"; url: string };
+  annotations?: ContentAnnotations;
 }
 
 export type ToolCallStatus =
@@ -67,6 +77,7 @@ export interface ToolRequestContent {
   status: ToolCallStatus;
   /** Epoch ms when the tool call started executing (set on event receipt). */
   startedAt?: number;
+  annotations?: ContentAnnotations;
 }
 
 export interface ToolResponseContent {
@@ -75,20 +86,24 @@ export interface ToolResponseContent {
   name: string;
   result: string;
   isError: boolean;
+  annotations?: ContentAnnotations;
 }
 
 export interface ThinkingContent {
   type: "thinking";
   text: string;
+  annotations?: ContentAnnotations;
 }
 
 export interface RedactedThinkingContent {
   type: "redactedThinking";
+  annotations?: ContentAnnotations;
 }
 
 export interface ReasoningContent {
   type: "reasoning";
   text: string;
+  annotations?: ContentAnnotations;
 }
 
 export interface ActionRequiredContent {
@@ -99,12 +114,14 @@ export interface ActionRequiredContent {
   toolName?: string;
   arguments?: Record<string, unknown>;
   schema?: Record<string, unknown>;
+  annotations?: ContentAnnotations;
 }
 
 export interface SystemNotificationContent {
   type: "systemNotification";
   notificationType: "compaction" | "info" | "warning" | "error";
   text: string;
+  annotations?: ContentAnnotations;
 }
 
 export type MessageContent =